JPS59226674A - Power converter - Google Patents

Abstract

PURPOSE:To reduce the cost of a power source by recovering and accumulating energy stored during the operation in a current limiting reactor inserted into a DC circuit in a storage capacitor, and using it for a control power source of a power converter. CONSTITUTION:When a motor side converter 5 is operated, energy is stored in a current limiting reactor 4. When a GTO thyristor of a main switching element is interrupted, the energy stored in the reactor 4 is recovered and stored through a diode 21 in a storage capacitor 22. The both terminals of the capacitor 22 are connected to the input sides of a DC/DC converter 28. The converter 28 suitably converts the energy stored in the capacitor 22 and applies it to a power converter controller 9.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention utilizes energy stored in a current limiting reactor inserted into the DC power supply side of a power converter that supplies power for driving an electric motor to the power converter. The present invention relates to a power conversion device that is used as a power source for controlling a device.

[Prior art and its problems]

FIG. 1 is a circuit diagram of a known inverter device that rectifies alternating current power and then converts it into alternating current with variable voltage and variable frequency to operate an induction motor at variable speed.

In Fig. 1, AC power from an AC power supply is converted into DC by a main rectifier 2, this DC is smoothed by a main smoothing capacitor 3, and then converted to a variable voltage 1 by a converter 5 on the motor side via a current limiting reactor 4. - Converted to variable frequency AC power and supplied to the AC motor 6, which is the load.

The motor-side converter 5 is generally operated using a pulse width modulation method to adjust its output voltage and output frequency.
Along with this operation, the main switching element (GTO thyristor in the case of FIG. 1) of the motor-side converter 5 intermittents the current.

A current limiting reactor 4 inserted into the DC circuit is a stagnation reactor connected in antiparallel to a GTO thyristor which is a main switching element of a motor side converter 5.

In order to suppress the reverse current flowing through the iode, and when the DC side is short-circuited due to commutation failure, the rate of increase in DC current d
This is to suppress i/dt and facilitate protection coordination. G which is the main switching element of the motor side converter 5
The energy stored in this current limiting reactor 4 as the TO thyristor intermittents the current flows through the diode 1.
1 and then collected and stored in the storage capacitor 12. The energy recovered and stored in this storage capacitor is returned to the main smoothing capacitor 3 by a chopper device (not shown) or the like to operate the motor 6.

On the other hand, the power necessary for the control section 9 for controlling the power converter including the motor-side converter 5 is supplied to the transformer 15 and the second rectifier 1 connected to a circuit branched from the AC power source 1.
6, and is obtained from the DC/DC converter 18 via the second smoothing capacitor 17. By the way, in the power conversion device that drives such a tie machine, the AC power supply 1 is short-time I',! ] (For example, about 1 second) It is desirable to continue operation even if there is a power outage. Rotational energy is stored in the operating AC motor 6 and the load connected to this motor 6, so even if the AC power supply 1 is briefly interrupted 5, the motor-side converter 5 must be appropriately controlled. If so, it is possible to continue operation. However, if the control unit 9 of the power conversion device that receives control power from the same AC power supply 1 stops operating due to a power outage, the electric motor 6 cannot continue operating. Therefore, if the capacitance of the second smoothing capacitor 17 is increased so that the energy stored in this capacitor 17 can be used during an AC power outage, a capacitor with an extremely large capacity will be required, and the device will become larger. It had the disadvantage of being uneconomical.

Another possible method is to obtain the control 1 power supply during a short power outage of the AC power supply 1 from a DC intermediate circuit located between the main rectifier 2 and the motor side converter 5, but generally the voltage of this circuit is high (6
Since it is often around 00 volts or more,
The DC/DC converter input voltage for creating the control power source also increases. Therefore, this DC/DC converter has the disadvantage of being complicated and expensive.

[Purpose of the invention]

The present invention provides a small and economical power supply means for the control unit so that the control unit of the power conversion device that supplies power to the motor does not interrupt its operation even if the power supply is interrupted for a short time. The purpose is to provide a power conversion device that can continue to operate.

[Key points of the invention]

In the present invention, electric power led from a DC power source via a smoothing capacitor and a current limiting reactor is converted and supplied to the electric motor by a converter on the motor side, and is stored in the current limiting reactor as the power conversion device operates. The above objective is achieved by storing the energy generated in the energy storage means and using this stored energy for controlling the power conversion device.

[Embodiments of the invention]

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

The details of the present invention will be explained below based on this embodiment.

In FIG. 2, AC power from a three-phase AC power source 1 is rectified by a three-phase full-wave rectifier 2, smoothed by a main smoothing capacitor 3, and then passed through a current limiting reactor 4 to a motor-side converter 5.
The role of the current limiting reactor 4 is as described above.

In this embodiment, the motor side converter 5 is configured by a bridge connection of a combination of a GTO thyristor and a feedback diode, but instead of the GTO thyristor, a normal thyristor, power transistor, electrostatic induction thyristor, etc. may be used. You can also do that. The motor-side converter 5 intermittents the DC power by chopping and supplies variable voltage/variable frequency AC power to the AC motor 6, so that the motor 6 is operated at an arbitrary rotation speed.

Energy is stored in the current limiting reactor 4 as the motor side converter 5 operates, and when the GTO thyristor, which is the main switching element, is shut off, the energy stored in the current limiting reactor 4 is transferred through the diode 21. It is collected and stored in the storage capacitor 22. Both ends of this storage capacitor 22 are connected to the input side of a DC/DC converter 28, and the converter 28 appropriately converts the energy stored in the storage capacitor 22 and supplies it to the power converter control section 9. In other words, in this power conversion device, the energy stored in the current limiter 6 and the reactor 4 during operation is the power source for the control unit 9, but since the entire device is computerized, the energy required for continued operation is is small,
It can be covered by the energy supplied from the current limiting reactor 4. In this case, if the capacity of the storage capacitor 22 is appropriately selected so that its terminal voltage becomes the optimum voltage (for example, 100 volts) for the DC/DC converter 28,
Since this DC/DC converter 28 can use a power transistor or the like that is easy to handle, the cost can be reduced.

By configuring the power converter control unit 9 to supply the necessary energy by the means described above, even if the AC power supply 1 is interrupted for a short time while the electric motor 6 is operating, the motor-side converter 5 can be controlled. The operation can be continued by adjusting the frequency relay so as to keep the magnetic flux of the lever electric motor 6 constant and causing the electric motor 6 to operate as a generator. That is, even if the AC power source 1 experiences a momentary power outage, the control power source is not lost, so there is no need to interrupt the operation. However, when the power converter is started, no energy is stored in the actuator 4 that flows I>B, and therefore the power converter cannot be controlled, so a separate starting control power source is required. A transformer 25 and a second rectifier 26 connected to a circuit branched from the AC power supply 1 are the starting control power supply, and the DC output of the transformer 25 and the second rectifier 26 are connected to both ends of the storage capacitor 220 described above. If the output voltage is set to be slightly lower than the voltage across the storage capacitor 220, this starting control power supply will supply power to the DC'/DC comparator 28 during startup, but once it is in operation, This D
The power supplied to the C/DC converter 28 is automatically switched to the energy stored in the current limiting reactor 4.

That is, since the starting control power source is used only for a short time when the power converter is started, the transformer 25 and the second rectifier 26 can be kept at the rated voltage for a short time, resulting in a small and low-cost product.

The embodiment of the present invention shown in FIG. 2 describes a case where the motor-side converter 5 is an inverter that converts direct current to alternating current and drives the AC motor 6. However, the motor-side converter 5 may be a chopper. It goes without saying that similar effects can be achieved even when a DC motor is driven by a DC motor, and this is, of course, included in the present invention.

[Effects of the Invention] According to the present invention, the energy stored in the current limiting reactor inserted into the DC circuit during operation is recovered and stored in the storage capacitor, and this is configured to be used as a control power source for the power converter. Since the frost pressure can be freely selected, the cost of the power supply device can be reduced, and even if the power supply is interrupted for a short time, the control power supply is not lost, so the motor can continue to operate. Furthermore, since the starting control power source is also small and inexpensive, the cost of the control power source for the power converter is lower than that of conventional devices, and the functionality is improved because operation can continue even if the power supply is interrupted for a short time.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional power conversion device, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1... AC power supply, 2... Main rectifier, 3
...Main smoothing capacitor, 4...Current limiting reactor, 5...Electrical 9-Motor side converter, 6...AC motor, 9...・
...Power converter control unit, 11.21...Diode, 12.22...Storage capacitor, 15
．． 25...Transformer, 16°26...Second rectifier, 17...Second smoothing capacitor, 18
．． 28...D C/DC converter. 10-

Claims (1)

[Claims] In a power converter device, in which electric power led from a DC power supply via a smoothing capacitor and a current limiting reactor is converted into electric power desired by a motor by a converter on the motor side and supplied to the electric motor, the It is characterized by comprising an energy storage means for recovering and storing the energy stored in the current limiting reactor, and a means for using the energy stored in the energy storage means for controlling the power conversion device. Power converter.